Refrigeration compressor with internal cooling system

ABSTRACT

A refrigeration compressor includes an internal cooling system. The compressor includes a compressor shell ( 1 ), inside of which are disposed a compression cylinder ( 2, 3 ), a piston that performs an alternating movement inside the cylinder, an oil accumulation region ( 5 ) in the lower part of the compressor shell, and piston drive means having a rotary shaft ( 4 ) oriented substantially vertically, with an upper end mounted to a piston drive cam ( 7 ). The compressor has a system for collecting the oil coming from the shaft ( 4 ), and expelled by the cam ( 7 ), in the upper part of the shell ( 1 ). This accumulated oil is drained over the compression cylinder ( 2, 3 ), so as to cool it, thus increasing the efficiency of the compressor.

The present invention refers to hermetic refrigeration compressors, withreciprocal movement, which have means for collecting oil which isexpelled by the drive shaft by way of the cam, in the upper part of thecompressor shell. This accumulated oil is used to cool certain specificparts of the compressor block so as to increase the efficiency thereof.Thereafter, the oil returns to the bottom of the compressor.

DESCRIPTION OF THE STATE OF THE ART

Attempts to improve the performance of refrigeration compressors areincreasingly common, the main purpose being to reduce their energyconsumption. It is known that a large part of the losses of compressorsare due to the overheating of gas in the path from the entry of thecompressor up to the entry of the compression cylinder. Another factorthat reduces the performance of compressors is the inefficiency of gascompression, due to the high working temperature of the cylinder.

Accordingly, with the aim of increasing the efficiency of thecompressors, ideas and solutions have been developed viewing thereduction of the temperature of the cylinder. Different approaches withthis objective can be found in the patent documents described ahead.

For example, patent document WO 2007/068072, uses the concept ofisolation of cylinder heating sources. According to this document, aspacing duct is built on a valve plate and open to the interior of thedischarge chamber, maintaining the cylinder cover of the compressorspaced from the valve plate and defining an annular plenum around saidspacing duct. Accordingly, the heat transmission from the cylinder coverto the valve plate is reduced, ultimately reducing the heating of thecylinder in the compression chamber region, increasing the efficiency ofthe compressor.

Document WO 2007/014443 proposes another solution to increase theefficiency of compressors, which uses heat tubes to remove the heat fromthe hot parts in contact with the cylinder. This document proposes ahermetic compressor with a heat dissipation system, in which a thermalenergy transfer duct is mounted to the cylinder block, the duct having aheat absorbing end, whereas its other heat releasing end is disposedaway from the cylinder block in order to absorb heat generated with thecooling fluid compression inside the cylinder and dissipate it to aregion away from the cylinder, thus reducing the temperature of thecylinder, and also increasing the efficiency of the compressor.

Another possible alternative to reduce the temperature of the cylinderis the best use of lubricating oil of the compressor as cooling means.Currently, the main function of the oil is to lubricate the mechanism ofthe compressor, in order to guarantee the reliability and durability ofits parts.

Based on the use of oil with cylinder cooling objectives, we can citeU.S. Pat. No. 4,569,639, in which the inventors proposed the use of anoutlet extension of the shaft and a deflector in the cylinder head, withthe objective of directing the flow of oil leaving the shaft extensiontowards the cylinder head, causing cooling of the cylinder. Thisextension of the cylinder has an orifice through which the oil is slunghorizontally towards the deflector of the cylinder head, whereas thisextension is turned. The deflector also has an orifice at a heightapproximately equal to the height at which the oil is slung, making thisoil run over the cylinder head to cool it. Additionally, this inventionallows a reduction of the oil, to prevent it from boiling and losing itsessential properties.

The inventors indicate that the objective of the invention is to reducethe temperature of the cylinder, to provide greater reliability of thecompressor, because a cooler cylinder would reduce the risks ofexcessive heating of the oil that is found in the inner region of thiscomponent, thus avoiding possible problems of carbonization of this oil,which could generate residues which would damage the compressor.

OBJECTIVES OF THE INVENTION

An objective of the invention is to provide an increase in theefficiency of hermetic refrigeration compressors, maximizing the flow ofoil around the compressor cylinder and at the same time reducing theworking temperature of the cylinder.

Another objective of the invention is to reduce overheating of thecompression gas, further contributing to boost the efficiency of thecompressor.

BRIEF DESCRIPTION OF THE INVENTION

The objectives of the invention are achieved by means of a refrigerationcompressor with an internal cooling system, comprising compressor shell,inside of which are disposed a compression cylinder having a cylinderbody and a cylinder head, a piston that performs an alternating movementinside the cylinder, an oil accumulation region in the lower part of thecompressor shell, piston drive means that drive the alternating movementof the piston inside the cylinder, and means for pumping oil from theoil accumulation region over the piston drive means, and the compressorshell comprises an oil sump located in its internal upper portion, theoil sump having an oil drain directed on the surface of the cylinder.

Preferably, the oil sump extends around the entire inner circumferenceof the shell, and the oil drain from the oil sump is intended forspilling oil over the cylinder body.

The compressor shell may comprise a cover, and the oil sump is formed inthe region of this cover, and can be formed integrally with the cover,or integrally with the compressor shell, or as an additional part whichis coupled to a part of the compressor shell. The oil sump can be formedby stamping during the production process of a part of the compressorshell.

The piston drive means comprise a rotary shaft oriented substantiallyvertically, which has an upper end mounted to a piston drive cam, whichexpels the oil pumped over the piston drive means. The oil sumppreferably comprises an oil collection region, in which at least aportion of the oil is collected that is expelled by the piston drivemeans, and the oil collection region has a geometry that allows therun-off of the oil collected to drain from the oil sump.

SUMMARIZED DESCRIPTION OF THE DRAWINGS

The present invention shall now be described in further details based ona sample embodiment represented in the drawings, wherein the figuresshow:

FIG. 1—is a cross-sectional view of a refrigeration compressor of thestate of the art, without the inner cooling system of the presentinvention; and

FIG. 2—is a cross-sectional view of a refrigeration compressor accordingto a present invention, with the inner cooling system.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a compressor of the state of the art merely forcomparison purposes with the present invention. This compressor of thehermetic refrigeration compressor type, with reciprocal movement doesnot have the internal cooling system of the present invention. Thiscompressor is disposed inside the shell 1. The compressor comprises acylinder that has a cylinder body 3 and a cylinder head 2, and a pistonthat performs an alternating movement inside the cylinder. In the lowerportion of the compressor shell, an oil accumulating region 5 is formedin the shape of a well. The oil accumulating in this accumulation regionoriginally has the purpose of lubricating the compressor parts, reducingthe attrition between them and increasing the durability of thecompressor.

This refrigeration compressor of the state of the art also has pistondrive means, which are responsible for driving the alternating movementof the piston inside the cylinder, compressing the compression fluid.The drive means normally comprise a rotor and a stator, which drive therotational movement of a rotary shaft 4. This rotary shaft is orientedsubstantially vertically in relation to the compressor shell, and isdisposed in such a way that its lower end 13 is immersed in the oilwell, while its opposite upper end is mounted to a cam 7 which drivesthe piston movement.

Therefore, when the compressor is switched on and the rotary shaft 4turns inside the compressor, an oil pump pumps the oil upwards that isaccumulated in the oil accumulation region 5, towards the drive means,and particularly around the rotary shaft 4, such that a portion of theoil 14 is ultimately slung to the upper part of the shaft, by means ofthe also rotational cam 7. As shown by the arrows in FIG. 1, thisportion of oil is aimed upwards, towards the upper face of thecompressor shell 1, or on the inner surface of the cover of thecompressor 6, and also sidewards, towards the inner walls of the upperregion of the compressor shell. Another portion of oil expelled over thecam around the area formed between the compressor block and the upperface of the shell falls again and runs over the compressor block as awhole.

Thus, a large part of the oil 14 that is slung towards the upper face ofthe compressor shell 1 ultimately runs towards the ends of this upperface or cover 6, and then runs downwards over the side walls of theshell, falling again onto the oil accumulation region 5, where itexchanges heat with the compressor shell 1. There is an optimization ofconcentration of the oil expelled over the cylinder, to cool this partof the compressor specifically.

However, experimental analyses indicate that there is a considerabledifference of temperature between the oil present in the oilaccumulation region 5 at the bottom of the compressor (also calledcarter) and the compression cylinder, and the oil is considerably coolerthan the compression cylinder. Accordingly, there is potential to reducethe temperature of the cylinder, if it is possible to maximize the flowof oil around it, withdrawing heat from its surface. A cooler cylindergenerates an improvement in efficiency of the compression process, andalso a decrease in the overheating of the gas during suction and thisreflects directly in an increase in the efficiency of the compressor. Inlight of this, the present invention proposes to maximize the flow ofoil on the cylinder in order to cool it.

FIG. 2 illustrates a compressor according to the present invention,which is provided with the internal cooling system. This compressor hasthe same parts described for the compressor of the state of the art,namely the shell 1 inside of which the compressor is disposed, thecylinder which has a cylinder body 3 and a cylinder head 2, and a piston12 that performs an alternating movement inside the cylinder. The oilaccumulation region 5 is also formed by the lower portion of thecompressor shell 1.

The refrigeration compressor according to the invention also has pistondrive means, which drive the alternating movement of the piston insidethe cylinder, and which comprise, for example, a motor and a statorwhich drive a rotary shaft 4 oriented substantially vertically inrelation to the compressor shell. The lower end of the shaft 13 isimmersed in the oil well, whereas its opposite upper end is mounted to acam 7 which drives the piston movement. This compressor also has apumping system which pumps the oil upwards that is accumulated in theoil accumulation region 5, towards the piston drive means, andparticularly around the rotary shaft 4, when the compressor is switchedon, such that a portion of the oil is expelled upwards, towards theupper face inside the compressor shell 1, or on the cover of thecompressor 6, and also sidewards, over the inner walls of the upperregion of the compressor shell, as shown by the arrows illustrated inFIG. 2. Another portion of oil expelled by the cam around the areaformed between the compressor block and the upper face of the shellfalls again and runs over the compressor block as a whole.

The compressor illustrated in FIG. 2 also comprises an oil sump 8located in the upper portion inside the compressor shell. This oil sump8 has an oil collection region 11 and an oil drain 9, which is directedto spill oil on the surface of the cylinder. Hence, the oil accumulatedon the sump 8, and having a temperature considerably lower than thetemperature of the cylinder, is drained so as to run on the surface ofthe cylinder, preferably on the surface of its body 3, so as to cool it.After this run-off, the oil returns to the oil accumulation region 5 inthe lower part of the compressor shell, where again it exchanges heatwith the shell 1.

Accordingly, there is a considerable increase in the flow of oil overthe cylinder, thus maximizing the cooling capacity of the cylinder bymeans of this portion of lubricating oil, which, normally according tothe state of the art, would run directly to the oil accumulation region5 at the bottom of the shell.

The oil sump preferably extends around the entire inner circumference ofthe compressor shell, and can be, for example, a circumferential wingthat extends from the inner wall of the compressor shell towards thecenter, and has an edge 10 extending vertically upwards from its innerend. The area formed on the circumferential wing and limited by the edge10 forms the oil collection region 11. Therefore, the oil 14 that wasexpelled from the cam 7 on the upper face of the compressor shell 1,will drop or run down over the oil sump 8, accumulating in the oilcollection region 11, and prevented from leaking out of the sump 8 bythe vertical edge 10. A portion of the oil 14 expelled by the cam aroundthe area formed between the compressor block and the upper face of theshell can also be collected by the oil sump 8.

As shown in FIG. 2, the oil drain 9 is built, for example, in the shapeof a wing inclined downwards from an end of the oil sump 8, in aposition above the compression cylinder, such that the drain 9 isdirected to spill oil onto the surface of the cylinder, and preferablyonto the surface of the cylinder body. Alternatively, the drain can alsobe built in the form of a hole on the surface of the oil sump 8 or onits edge, or in any other form that is capable of draining the oilaccumulated in the oil sump 8 over the surface of the cylinder of thecompressor. The oil collection region 11 is preferably shaped withgeometry such that it allows or facilitates the run-off of the oilcollected for draining 9 the oil sump, for example, with a horizontalcircumferential wing which can be slightly inclined downwards towardsthe drain region 9.

In an embodiment of the invention, as illustrated in FIG. 2, thecompressor shell preferably comprises a cover 6 in its upper part. Thus,the oil sump 8 can be formed directly in the region of this cover 6,being mounted thereon in the form of an additional part, or formedintegrally and jointly to the cover 6 in the form of a single part.

Alternatively, the oil sump 8 can be formed as an additional partmounted directly on the compressor shell 1 in its upper region, or fixedto any other part of this shell, for example being fixed to its innerside walls. In another embodiment of the invention, the oil sump 8 isformed integrally and jointly with the compressor shell.

When the oil sump 8 is built integrally and jointly with any part of theshell 1 of the compressor, be it with the cover 6 or other part of theshell body, this sump can be formed by means of additional steps in theprocess of stamping of these parts, during the production processthereof.

Additionally, in another alternative embodiment of the invention notillustrated in the drawings, the compressor may also comprise anoil-cooling device disposed in the upper oil sump 8. This device shouldbe able to cool the oil accumulated in the sump, before this oil fallsonto the cylinder, thus boosting the temperature reductions of thiscylinder. This cooling device can be in the form of a heat exchanger, aheat tube or any other means of cooling oil.

Having described an example of a preferred embodiment, it should beunderstood that the scope of the present invention encompasses otherpotential variations, being limited solely by the content of the claimsappended hereto, other possible equivalents being included therein.

1. A refrigeration compressor comprising an inner cooling system, saidcompressor comprising a compressor shell, inside of which are included:a compression cylinder comprising a cylinder body (3) and a cylinderhead (2), a piston (12) that performs an alternating movement inside thecylinder, an oil accumulation region (5) in the lower part of thecompressor shell, piston drive means that drive the alternating movementof the piston inside the cylinder, oil pumping means for pumping oilfrom the oil accumulation region (5) over the piston drive means,wherein the compressor shell (1) comprises an oil sump (8) located inits an internal upper portion, the oil sump comprising an oil drain (9)directed on the surface of the cylinder.
 2. The refrigeration compressoraccording to claim 1, wherein the oil sump (8) extends around the entireinner circumference of the compressor shell (1).
 3. The refrigerationcompressor according to claim 1, wherein the oil drain (9) of the oilsump is directed to spill oil onto the cylinder body (2).
 4. Therefrigeration compressor according to claim 1, wherein the compressorshell (1) comprises a cover (6), and the oil sump (8) is formed in theregion of the cover.
 5. The refrigeration compressor according to claim4, wherein the oil sump is formed integrally with the cover (6).
 6. Therefrigeration compressor according to claim 1, wherein the oil sump (8)is formed integrally with the compressor shell (1).
 7. The refrigerationcompressor according to claim 1, wherein the oil sump is formed bystamping during the production process of a part of the compressor shell(1).
 8. The refrigeration compressor according to claim 1, wherein theoil sump is built as an additional part which is coupled to a part ofthe compressor shell.
 9. The refrigeration compressor according to claim1, wherein the piston drive means comprises a rotary shaft (4) orientedsubstantially vertically, which has an upper end mounted to a pistondrive cam (7), through which the oil pumped over the piston drive meansis expelled.
 10. The refrigeration compressor according to claim 1,wherein the oil sump comprises an oil collection region (11), in whichat least a portion of the oil is collected which is expelled by thepiston drive means.
 11. The refrigeration compressor according to claim10, wherein the oil collection region (11) has a geometry that allowsthe run-off of the oil collected for draining (9) the oil sump (8). 12.The refrigeration compressor according to claim 1, further comprising anoil cooling device disposed in the oil sump (8).
 13. The refrigerationcompressor according to claim 2, wherein the oil drain (9) of the oilsump is directed to spill oil onto the cylinder body (2).
 14. Therefrigeration compressor according to claim 2, wherein the compressorshell (1) comprises a cover (6), and the oil sump (8) is formed in theregion of the cover.
 15. The refrigeration compressor according to claim14, wherein the oil sump is formed integrally with the cover (6). 16.The refrigeration compressor according to claim 3, wherein thecompressor shell (1) comprises a cover (6), and the oil sump (8) isformed in the region of the cover.
 17. The refrigeration compressoraccording to claim 16, wherein the oil sump is formed integrally withthe cover (6).
 18. The refrigeration compressor according to claim 2,wherein the oil sump (8) is formed integrally with the compressor shell(1).
 19. The refrigeration compressor according to claim 2, wherein thepiston drive means comprises a rotary shaft (4) oriented substantiallyvertically, which has an upper end mounted to a piston drive cam (7),through which the oil pumped over the piston drive means is expelled.20. The refrigeration compressor according to claim 3, wherein thepiston drive means comprises a rotary shaft (4) oriented substantiallyvertically, which has an upper end mounted to a piston drive cam (7),through which the oil pumped over the piston drive means is expelled.